Anatoly Miroshnichenko
Current research interests and recent results
More details about my research
Photometric, polarimetric, and spectroscopic studies of early-type
emission-line stars (1984-present)
This is the most important project in my research practice, all new
projects are connected with it. It is devoted to study of Herbig Ae/Be
stars and related objects which were recently called ``The Herbig Ae/Be
stellar group" by The et al. (1994, A&AS, 104,
315). I obtained more than 1000 multicolor photometric, several
hundreds polarimetric, more than 200 medium- and high-resolution
spectroscopic observations for nearly 100 such objects since 1984.
Since 1996 I have been collecting photometric observations for more
than 150 objects of ``The Herbig Ae/Be stellar group". The data base
contains more than 20000 optical, nearly 1500 infrared observations,
and includes high-resolution IRAS maps for almost all extended objects
of this group. Results of this study have been published in more than
30 papers and presented at 10 international conferences. A
review of photometric, polarimetric, and interferometric observations of
galactic B[e] stars has been presented at the Workshop on B[e]
stars held at the Institute d'Astrophysique de Paris, 1997 June 9-12.The
main results obtained so far can be summarized as follows:
Statistical studies.
- Evolution of the infrared excesses of pre-main-sequence and
main-sequence A-type stars has been studied (Miroshnichenko et al.,
Astron. Rep., 1996, 40, 509). A scenario of evolution of the
circumstellar dusty envelopes around 2-4 solar masses young stars is
proposed.
- A group of nearly 15 B-type emission-line stars with large
IR-excesses and IRAS fluxes rapidly decreasing towards longer
wavelengths has been separated and studied (Miroshnichenko,
Corporon, Sheikina, 1999, BAAS, 31, 845 ). It was shown that
these objects are most likely evolved binary stars with compact
companions. A study of 2 new candidates to this group, HD 85567
and Hen3-140, was presented at the 196 AAS Meeting in Rochester,
NY (Miroshnichenko
et al., 2000. BAAS, 32, 862). A study of another 2 stars from
this group, AS 78 and MWC 657, observed with different
techniques for the first time is presented in Miroshnichenko et al.,
2000 (A&AS, 147, 5).
Modeling.
- The spectral energy distributions of a number of Herbig Ae/Be
stars were fitted in detail for the wavelength range from 0.15 microns
to 2 millimeters using models containing a spherical optically-thin
envelope and an optically-thick geometrically-thin disk. The study
amplifies results of recent infrared imaging of some Herbig Ae/Be stars
that extended envelopes, optically thin at IR wavelengths, dominate the
IR emission from these objects, while optically thick accretion disks
give an important contribution to the observed radiation in the sub-mm
and millimetric wavelength range. It was shown that the disk gets
additional heating from the envelope that changes its spectrum (Miroshnichenko,
Ivezic, & Elitzur, 1997, ApJ, 475, L41 ; Miroshnichenko
et al 1999, ApJ, 520, L115 ) .
Individual stars.
- Two stars at the end of their pre-main-sequence life, HD 35929
and HD 203024, have been studied for the first time
(Miroshnichenko et al., Pis'ma v Astron.Zhurn., 1997, 23, 118). A new
photometric and first high-resolution spectroscopic study of another
Herbig Ae star, IP Per, is performed (Miroshnichenko et al.
2001, A&A, 377, 854).
- Several new early-type stars with large infrared excesses have
been discovered by identification of the objects from the Catalogue of
the galactic emission-line stars (Wackerling 1970, Mem.Roy.Astron.Soc.,
73, 153) in the IRAS Point Source Catalog. A study of the Herbig
Ae/Be candidates MQ Cas, BD+11 820, GSC 1181-0767, V1012 Ori, HDE
244604, HDE 290380, AS 116, and AS 117 is accomplished ( Miroshnichenko
et al. 1999, A&A, 347, 137).
- Continuum spectral energy distribution and emission-line spectrum
of a B[e] star MWC 314 were interpreted in the framework of an
LBV or a very luminous supergiant model (Miroshnichenko
1996, A&A, 312, 941 ; Miroshnichenko
et al. 1998, A&AS, 131, 469 ). This object is suggested to
be the second known galactic LBV candidate in the northern hemisphere
after P Cyg. Another peculiar high-luminosity object, also a possible
LBV candidate, AS 314 is studied in detail for the first time
(Miroshnichenko, Klochkova, Chentsov, 2000, A&AS, 144, 379).
- New estimate of HL Tau spectral type: possible early-type
massive pre-main-sequence star instead of a T Tau star (Yudin &
Miroshnichenko 1988, Astrofizika, 28, 91). Only in 1994 HST
observations showed that we do not see a star in that direction but
rather scattered light from an invisible object. New two-dimensional
modeling predicts a high-mass star at the center of this nebula.
- Discovery of periodical photometric and polarimetric variations
of a B[e] star MWC 342 (Bergner, Miroshnichenko, Sudnik, et al.
1990, Astrofizika, 32, 109). More recent study of this
remarkable source is published in Miroshnichenko
& Corporon 1999, A&A, 349, 126.
Spectropolarimetric and spectroscopic studies of circumstellar
geometries of early--type stars
This project is aimed at constraining geometries and orientations of
gaseous envelopes of classical Be and Herbig Ae/Be stars as well as at
investigation of a possible link between these groups. Evolutionary
connections of lower-mass Herbig Ae stars and their descendants, Beta
Pictoris stars, are also in the focus of this program (planet
formation, transition objects, stellar wind and circumstellar envelope
evolution). Extended model calculations of spectral line profiles are
planned along with spectroscopic and spectropolarimetric monitoring of
a large sample of these stars. Spectropolarimetric data in the UV
spectral region have been obtained in the space shuttle missions Astro-1,2(Wisconsin
Ultraviolet Photo-Polarimeter Experiment, WUPPE) while the optical data
are from previous and ongoing observations with the HPOL
spectropolarimeter of the University of Wisconsin. High-resolution
spectroscopy in the H-alpha region is currently obtaining at the Ritter
Observatory of the University of Toledo.The project has been started in
1997 June and the following results have been obtained so far.
- Two new classical Be stars (HD 4881 and HD 5839)
and two young main sequence stars (HD 184761 and HD 224648)
have been discovered using high-resolution spectroscopy. Strong
variations of the H-alpha profile of a Herbig Ae/Be star candidate HD
179218 similar to those of a classical Be star ZetaTau have been
detected for the first time. These results provide evidence for an
evolutionary link between pre-main-sequence Herbig Ae/Be stars and more
evolved classical Be stars (Miroshnichenko et al. 1999, MNRAS.
302, 612).
- Strong variations of the H-alpha line associated with an extended
period of strong emission during summer and fall 1997 have been
observed in a Herbig Be star HD 200775. The line equivalent
width took on the highest value reported in the last 20 years. A review
of the observational literature dating back to 1977 indicates periodic
behavior of the H-alpha equivalent width with a period of 3.68 years.
The next high emission state is predicted to occur in the first half of
2001 (Miroshnichenko et al. 1998, PASP, 110, 883). A
continuation of this study including results of the radial velocity
variations is published in Pogodin,
Miroshnichenko, Bjorkman, et al., 2000, A&A, 359, 299.
- Periodic radial velocity variations of different spectral lines
of classical Be stars Pi Aqr and Zeta Tau were discovered
using the Ritter Observatory data archive. The results have been
presented at the 196 AAS Meeting in Rochester, NY (Bjorkman
et al. 2000, BAAS, 32, 861). In particular, a period of 84.3
days in the H-alpha line radial velocity variations of Pi Aqr
was found. As a result, this object was proven to be a binary system
with a mass ratio of 6 (Bjorkman,
Miroshnichenko, et al. 2002, ApJ, 573, 812).
- Spectropolarimetric data on two Herbig Ae/Be stars, AB Aur
and HD 163296, have been studied.
- A spectroscopic study of a recent mass loss outburst of a bright
binary system Delta Sco associated with a periastron passage
resulted in a refinement of the orbital solution (Miroshnichenko et al.
2001, A&A, 377, 485)
Circumstellar envelopes of Herbig Ae/Be and related stars:
medium-resolution spectroscopy (1989-1991)
- Interpretation of the spectral and photometric characteristics of
a young stellar object VY Mon. Some evidences have been shown
that this star is a FU Ori object (Miroshnichenko, Yudin, & Jakubov
1992, A&ATr, 1, 211).
- Interpretation of the spectral and photometric characteristics of
a Herbig Ae/Be star MWC 297, a B[e] star MWC 84, and an
emission-line star MWC 930. Their observational characteristics
were explained in the framework of a binary system model containing an
early-type dwarf and a late-type giant star (Miroshnichenko 1994, ASP
Conf. Ser., 62, 134, Miroshnichenko 1995, A&ATr,6,
251). A recent X-ray outburst of MWC 84 (CI Cam) has
become evidence for its binary nature (Clark, Miroshnichenko,
Larionov, et al., 2000, A&A, 356, 50). New high-resolution
observations we obtained for CI Cam at the 6-meter Russian
telescope showed a triple-peaked structure of most of the emission
lines. The available estimates of the basic parameters of CI Cam
were analysed and methods to verify them were suggested (Miroshnichenko
et al., 2002, A&A, 390, 627).
Photometric behavior of classical Novae near maximum brightness
(1985-1987)
- A new method of interstellar extinction determination towards
Novae based on averaged color-indices obtained during their early
decline (Miroshnichenko 1988, Astron.Zhurn. (Soviet Astronomy),65,
582).
Other results